Modular patient support system

ABSTRACT

A radiation treatment system ( 100 ) for accurately delivering radiation to a targeted site within a cancer patient ( 108 ) that includes a modular patient support system and a patient positioner ( 114 ). The modular patient support system includes a modularly expandable patient pod ( 200 ) and at least one immobilization device, such as, for example, a rigid moldable foam cradle ( 350 ). The patient pod ( 200 ) includes a generally hemi-cylindrical support shell ( 212 ) that extends longitudinally between proximal edge ( 214 ) and distal edge ( 216 ), and transversely between two lateral edges ( 222, 224 ). In one embodiment, the lateral edges ( 222, 224 ) are tapered to minimize edge effects that result when radiation beams traverse the lateral edges ( 222, 224 ).

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/758,645, filed Apr. 12, 2010, which is a continuation of U.S.application Ser. No. 11/671,922, filed Feb. 6, 2007, now U.S. Pat. No.7,696,499, which is a continuation of U.S. application Ser. No.10/917,022, filed Aug. 12, 2004, now U.S. Pat. No. 7,173,265, whichclaims priority to U.S. Provisional Application No. 60/494,699, filedAug. 12, 2003, and to U.S. Provisional Application No. 60/579,095, filedJun. 10, 2004. The disclosures of all of the above-referenced priorapplications, publications, and patents are considered part of thedisclosure of this application, and are incorporated by reference hereinin their entirety.

GOVERNMENT SUPPORT

This invention was made with United States Government support undergrants DAMD17-99-1-9477 and DAMD17-02-1-0205 awarded by the Departmentof Defense. The Government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to radiation beam therapy systems, andmore particularly to a radiation treatment system with a patientpositioner. The present invention relates to radiation beam therapysystems, and more particularly to a modular patient support system. Thepresent invention relates to radiation beam therapy systems, and moreparticularly to a patient pod with tapered edge configurations thatreduce edge effects associated with abrupt changes in the waterequivalency in the radiation beam path.

2. Description of the Related Art

Radiation therapy systems are known and used to provide treatment topatients suffering a wide variety of conditions. Radiation therapy istypically used to kill or inhibit the growth of undesired tissue, suchas cancerous tissue. A determined quantity of high-energyelectromagnetic radiation and/or high-energy particles are directed intothe undesired tissue with the goal of damaging the undesired tissuewhile reducing unintentional damage to desired or healthy tissue throughwhich the radiation passes on its path to the undesired tissue.

Proton therapy has emerged as a particularly efficacious treatment for avariety of conditions. In proton therapy, positively charged protonsubatomic particles are accelerated, collimated into a tightly focusedbeam, and directed towards a designated target region within thepatient. Protons exhibit less lateral dispersion upon impact withpatient tissue than electromagnetic radiation or low mass electroncharged particles and can thus be more precisely aimed and deliveredalong a beam axis. Also, upon impact with patient tissue, protonsexhibit a characteristic Bragg peak wherein a significant portion of thekinetic energy of the accelerated mass is deposited within a relativelynarrow penetration depth within the patient. This offers the significantadvantage of reducing delivery of energy from the accelerated protonparticles to healthy tissue interposed between the target region and thedelivery nozzle of a proton therapy machine as well as to “downrange”tissue lying beyond the designated target region. Depending on theindications for a particular patient and their condition, delivery ofthe therapeutic proton beam may preferably take place from a pluralityof directions in multiple treatment fractions to maintain a total dosedelivered to the target region while reducing collateral exposure ofinterposed desired/healthy tissue.

U.S. Pat. No. 4,870,287, issued Sep. 26, 1989, assigned to the LomaLinda University Medical Center, titled MULTI-STATION PROTON BEAMTHERAPY SYSTEM, describes and illustrates a radiation beam therapysystem. The system described therein includes several differenttreatment stations, each including a gantry for supporting and rotatinga radiation beam transport and delivery system on an axis of rotationaround a stationary patient to deliver a treatment beam to apredetermined target isocenter within the patient from several differentangles.

With many radiation treatment systems and protocols, a unique treatmentplan is first developed for each cancer patient. For example, in thedevelopment of a treatment plan, such as, for example, proton radiationtreatment, the patient is generally positioned on a support table orsupport structure and the internal anatomy of the patient's body scannedwith an imaging technique, such as, for example, computed tomography (CTScan). Images produced by the imaging device are analyzed to preciselylocate the cancer sites defining the targets for the radiation beams. Inmany cases, physicians develop a radiation treatment plan calling for anumber of different patient treatment sessions with radiation beams ofdifferent magnitudes, durations and angles of direction.

Given the high number of cancer patients who could benefit fromradiation treatment and the relatively few number of sophisticatedradiation (e.g., proton) treatment facilities and systems available inthe world, there is a need for radiation treatment providers to achievegreater patient throughput at their existing facilities. As such, thereis a need for patient support and positioning systems that utilizeautomated or robotic patient positioning devices, and thereby provideradiation treatment providers with the ability to achieve increasedpatient throughput.

For each treatment session, it is important that the patient besupported in the exact same position as during the preliminary imagingor scanning session utilized in the development of the treatment plan(i.e., the original position). Accordingly, there is a need for apatient positioning and repositioning support system for fixedlysecuring a patient in an original position during radiation treatmentand for repositioning the patient in the same original position duringany subsequent radiation treatment sessions. For certain applicationsthat involve irradiating different portions of a patient's anatomy fromseveral different angles, it is desirable for the patient positioningand repositioning support to fixedly secure the patient.

The radiation treatment protocol for any given patient can depend on anumber of factors, including, for example: the size and physicalcharacteristics of the patient; the type, size, and location of thetumor(s) being irradiated; and the aggressiveness of the treatmentprotocol. As such, there is a need for a modular patient support systemthat can be easily adjusted to accommodate a large number of treatmentprotocols.

For certain treatment protocols it is necessary to direct the radiationbeam at angles that traverse at least one lateral edge of the patientpod. Accordingly, there is a need for pod edge configuration thatreduces discontinuities in the strength or intensity of radiation beamsthat pass through or near a pod lateral edge.

SUMMARY OF THE INVENTION

In accordance with one embodiment described herein, there is provided aradiation treatment system for delivering prescribed doses of radiationto a targeted site within a cancer patient and for increasing patientthroughput levels. The treatment system includes: a patient treatmentstation; a gantry, a radiation beam source; a nozzle; a modular patientsupport system; a patient positioner; and a control system.

In one embodiment, the radiation beam source includes a source ofprotons and an accelerator for accelerating protons as a beam.

In accordance with one embodiment described herein, there is provided amodular patient support system for efficiently securing a cancer patientin a fixed position during radiation treatment. The support systemincludes a modular patient pod.

In accordance with one embodiment described herein, there is provided amodular patient pod for providing cantilevered support of a cancerpatient undergoing radiation treatment. The pod includes: alongitudinally-extending support shell; a proximal extension track; adistal extension track; and a positioner-pod connector.

In one embodiment, the support shell is made from a treat-throughmaterial, such as, for example, carbon fiber.

In one embodiment, a distal pod attachment is engaged with the distalextension track. In another embodiment, a proximal pod attachment isengaged with the proximal extension track.

In accordance with one embodiment described herein, there is provided amodular patient pod that is configured to reduce any edge effects. Thepod includes a support shell having a first lateral edge and a secondlateral edge.

In one embodiment, the first lateral edge includes a first tapered edgeand a first rail made from a first low-density material, such as, forexample, epoxy with microspheres. In another embodiment, the secondlateral edge includes a second tapered edge and a second rail made froma second low-density material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of one embodiment of a radiation therapysystem with a robotic patient positioning system.

FIG. 2 is a schematic diagram of another embodiment of a radiationtherapy system with a robotic patient positioning system.

FIG. 3 is a side isometric view of one embodiment of a robotic patientpositioner.

FIG. 4A is an isometric elevated side view of one embodiment of amodular patient pod.

FIG. 4B is a transverse cross-sectional view of the patient pod of FIG.4A.

FIG. 4C is a close-up cross-sectional view of the pod shell lateral edgeof FIG. 4B.

FIG. 5 is a transverse cross-sectional view of one embodiment of amodular patient support system.

FIG. 6 is an isometric elevated side view of one embodiment of apositioner-pod connector.

FIG. 7A is an isometric elevated side view of one embodiment of oneembodiment of a short, flat attachment.

FIG. 7B is an isometric elevated side view of one embodiment of a long,flat attachment.

FIG. 7C is an isometric elevated side view of one embodiment of a shellleg or head extension.

FIG. 7D is an isometric elevated side view of one embodiment of a flatextension that accommodates immobilization devices.

FIG. 7E is an isometric elevated side view of one embodiment of a short,head rest extension.

FIG. 7F is an isometric elevated side view of one embodiment of apositioner end extension.

FIG. 7G is an isometric elevated side view of one embodiment of a proneheadrest.

FIG. 8 is a schematic partial cross-sectional side view of oneembodiment of a modular patient support system and corresponding aimablevolumes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A. Radiation Treatment System with Robotic Patient Positioner

In accordance with one embodiment described herein, there is provided aradiation treatment system with a patient positioner.

Reference will now be made to the drawings wherein like referencedesignators refer to like parts throughout. FIG. 1 illustratesschematically one embodiment of a radiation therapy system 100. Theradiation therapy system 100 is designed to deliver therapeuticradiation doses to a target region within a cancer patient 108 fortreatment of malignant or other conditions from one or more angles ororientations with respect to the patient.

In one embodiment, the radiation therapy system 100 is designed todeliver therapeutic doses of proton beams to a target area within thepatient. Additional details on the structure and operation of such asystem 100 can be found in U.S. Pat. No. 4,870,287, titled MULTI-STATIONPROTON BEAM THERAPY SYSTEM, which is incorporated herein in its entiretyby reference. In another embodiment, the system 100 is designed todeliver any other clinically suitable form of radiation known in theart, such as, for example, x-rays, gamma rays, hadrons, neutrons, etc.

The radiation therapy system 100 typically includes a patient treatmentstation and a gantry 102 which includes a generally hemispherical orfrustoconical support frame for attachment and support of othercomponents of the radiation therapy system 100. Additional details onthe structure and operation of the gantry 102 can be found in U.S. Pat.No. 4,917,344 and U.S. Pat. No. 5,039,057, both titled ROLLER-SUPPORTED,MODULAR, ISOCENTRIC GENTRY AND METHOD OF ASSEMBLY, both of which areincorporated herein in their entirety by reference.

With continued reference to FIG. 1, in one embodiment, the system 100also comprises a nozzle 110 which is attached and supported by thegantry 102 such that the nozzle 110 may revolve relatively preciselyabout a gantry isocenter 120. The system 100 also comprises a radiationsource 106 delivering a therapeutic beam, such as a beam of acceleratedprotons which pass through and are shaped by an aperture 110 positionedon the distal end of the nozzle 110. The beam path is represented bynumeral 146. The aperture is preferably configured for the patient'sparticular prescription of therapeutic radiation therapy.

With continued reference to FIG. 1, the system 100 also comprises one ormore imagers 112 which, in this embodiment, is retractable with respectto the gantry 102 between an extended position and a retracted position.Here, the imager 112 is shown in the extended position. In oneembodiment, the imager 112 comprises a solid-state amorphous siliconx-ray imager which can develop image information such as from incidentx-ray radiation that has passed through a patient's body. The system 100also comprises an x-ray source 130 which selectively emits appropriatex-ray radiation which passes through interposed patient tissue so as togenerate a radiographic image of the interposed materials via the imager112. The retractable aspect of the imager 112 provides the advantage ofwithdrawing the imager screen from the beam path of the radiation source106 when the imager 112 is not needed thereby providing additionalclearance within the gantry 102 enclosure as well as placing the imager112 out of the path of potentially harmful emissions from the radiationsource 102 thereby reducing the need for shielding to be provided to theimager 112. In this embodiment, the imagers and radiation sources 130are arranged orthogonally to provide a radiographic images of thepatient from two directions.

The system 100 also comprises a patient positioner 114 and a patient pod200 which is attached to positioner-pod connector 234 at the distal,working end 116 of the patient positioner 114. The patient positioner114 is adapted to, upon receipt of appropriate movement commands,position the patient pod 200 in multiple translational and rotationalaxes and preferably is capable of positioning the patient pod 200 inthree orthogonal translational (i.e., the longitudinal, vertical, andlateral) axes as well as three orthogonal rotational (i.e., pitch, roll,and yaw) axes so as to provide a full six degrees freedom of motion toplacement of the patient pod 200.

It will be understood that the patient can be positioned in any numberof ways, including, but not limited to, automatic, semi-automatic (e.g.,with a hand pendent), manual controlled with direct interface to thepositioner controller, or full manual (e.g., releasing a brake andmoving each device axis with a hand crank).

With reference to FIGS. 2 and 3, in one embodiment, the patientpositioner 114 comprises a robotic arm 150, such as, for example, a KUKAKR500-L420 robot. In one embodiment, the KUKA KR500-L420 robot is safelymounted on a pedestal located in a pit beneath a rotating platform 132,and extends up through a cut-out 134 in the platform 132. The platform132 is generally flush with the treatment area floor 130. The roboticarm 150 can typically move in six degrees of freedom and has the reachnecessary to achieve all possible treatment positions in the gantry 102.The robotic arm 150 extends between a base 118 and a distal, working end116.

A swivel joint 152 at the distal end 116 of the robotic arm 150 iscapable of rotating any devices connected to its distal end in aclockwise or counterclockwise manner. The swivel joint 152 typicallyinterfaces with a positioner-pod connector 234, which in turn connectswith a patient pod 200. Robotic arm segment 162 and any distally locatedarm components are capable of being rotated about swivel joint 154.Robotic arm segment 164 and any distally located arm components arecapable of being rotated about swivel joint 156. Robotic arm segment 166and any distally located arm components are capable of being rotatedabout swivel joint 158. Robotic arm segment 168 and any distally locatedarm components are capable of being rotated about swivel joint 159.Robotic arm segment 170 and any distally located arm components arecapable of being rotated about swivel joint 160.

With reference to FIG. 2, in one embodiment, the radiation therapysystem 100 comprises an imager 112 that is in a retracted position orconfiguration, and thus hidden from view. The patient positioner 114 ismounted on a pedestal located in a pit beneath a rotating platform 132.The platform 132 is generally flush with the treatment area floor 130and generally follows the rotational motion of the positioner 114 at thebase 118 of the positioner 114. The robotic arm 150 of the positioner114 extends up through a cut-out 134 in the platform 132. In oneembodiment, shown in FIGS. 2 and 3, the platform 132 rotates in theclockwise or counterclockwise direction and follows the rotationalmotion about swivel joint 160.

With reference to FIGS. 2 and 5, in one embodiment, the radiationtreatment system 100 comprises a modular patient support system 199which interfaces with the patient positioner 114. More specifically, thedistal end 116 of the robotic arm 150 interfaces with a patient pod 200,described in further detail below.

The system 100 is under regulation and operator control through acontrol system that is generally patterned after the system used for theLoma Linda University Medical Center 200 MeV synchrotron facility. Thecontrol system provides an operator controllable system for controllingthe rotational position of the gantry 102, as well as the translationaland rotational position of the patient positioner 114. The controlsystem provides timing pulses to the entire system 100.

In one embodiment, the control system comprises multiple distributedmicroprocessor-based systems networked together and to a workstationcomputer using a Local Area Network (LAN) Standard. The LAN is anEthernet based protocol. The workstation performs the centralizedcoordination of beam requests from the treatment stations in the therapysystem as well as programmed beam-energy control.

Additional details on the structure and operation of the radiationtherapy systems can be found in commonly assigned applications—namely,U.S. Pat. No. 7,280,633, issued on Oct. 9, 2007, titled PATH PLANNINGAND COLLISION AVOIDANCE FOR MOVEMENT OF INSTRUMENTS IN A RADIATIONTHERAPY ENVIRONMENT, and U.S. Pat. No. 7,199,382, issued on Apr. 3,2007, titled PATIENT ALIGNMENT SYSTEM WITH EXTERNAL MEASUREMENT ANDOBJECT COORDINATION FOR RADIATION THERAPY SYSTEM, the contents of eachof which are hereby incorporated in their entirety into this disclosureby reference.

B. Modular Patient Support System:

In accordance with the one embodiment described herein, there isprovided a modular patient support system that generally comprises amodular patient pod and an immobilization device.

FIGS. 4A and 4B illustrate one embodiment of a modular patient pod 200for radiation therapy. The pod 200 comprises a longitudinally extendingshell structure 212. In the present embodiment, the positioner-podconnector 234 is offset from the middle of the shell structure 212,thereby resulting in a pod 200 that is cantilevered with respect to theworking end 116 of the patient positioner 114. A pod 200 that iscantilevered with respect to the positioner 114 advantageously allowsmore ways to position the patient within the radiation therapy system100. A cantilevered pod 200 advantageously reduces the chances ofcollisions with other components of the system 100 as the pod 200 and/orpositioner 114 or adjusted within the system 100. A pod 200 that iscantilevered can also facilitate the entry or placement of the patientinto the pod 200. In another embodiment (not illustrated), the connector234 is located, along the longitudinal axis of the pod 200, at or nearthe middle of the shell structure 212.

The pod 200, any components thereof, and any extensions or attachmentsthereto, are described herein with reference to the section of the pod200 which interfaces with the patient positioner 114 via apositioner-pod connector 234. Any components, extensions, andattachments that are closer, along a visualized longitudinal axis of thepod 200, to the connector 234 are referred to herein as being proximal,while any components, extensions, and attachments located toward theopposite end of the pod are referred to herein as being distal.

The longitudinally extending shell structure 212 extends between a shellproximal edge 214 and a shell distal edge 216. The shell 212 has atransverse concave top surface 218 and a transverse concave bottomsurface 220. The shell 212 transversely extends between a firstupwardly-extending lateral edge 222 and a second upwardly-extendinglateral edge 224.

With reference to FIGS. 4A and 4B, in one embodiment, the support shell212 is a hemi-cylindrical structure acting as a cantilevered support forpatients during radiation treatment. Here, the hemi-cylindrical shape ofthe shell 212 facilitates providing enhanced physical support andconsistent indexing when used with immobilization devices, such as, forexample, foam inserts or vacuum bags, described in further detail below.The curved shape of the pod 200 also permits beam shaping devices to belocated near the patient.

The patient can be positioned in the patient pod 200 in any number ofpositions. In one approach, where the patient is positioned in the pod200 in a supine position with his head near the shell distal edge 216and his feet near the shell proximal edge 214, the lateral edge 222 ison the patient's right-hand side while the lateral edge 224 is on thepatient's left-hand side. In another approach, where the patient ispositioned in the pod 200 in a prone position with his head near theshell distal edge 216 and his feet near the shell proximal edge 214, thelateral edge 222 is on the patient's left-hand side while the lateraledge 224 is on the patient's right-hand side. In yet another approach,where the patient is positioned in the pod 200 in a supine position withhis feet near the shell distal edge 216 and his head near the shellproximal edge 214, the lateral edge 222 is on the patient's left-handside while the lateral edge 224 is on the patient's right-hand side.

With reference to FIGS. 4A and 4B, in one embodiment the pod 200comprises attachment or extension tracks 226 and 228 that are located onshell edges 214 and 216, respectively. Extension tracks 226 and 228 cancomprise a known universal attachment mechanism, such as, for example, aplurality of linearly arranged apertures 230, 232 that facilitatecommunication between the top and bottom surfaces 218, 220 of the shell212. In one embodiment, one or more modular extensions are adjustablyfastened to the attachment tracks 226, 228 by means of removable pins orbolts slotted or screwed through the apertures 230, 232.

In one method of use, involving treatment near the patient's headregion, the patient is positioned with his head beyond shell edge 216 ona head rest extension 310 attached to track 228. In another method ofuse, involving treatment in the patient's lung region, the patient ispositioned head-first (i.e., head near shell edge 216) with hisshoulders inline with track 228 so that the radiation beam passesthrough the shell 212 and into the lung region. In yet another method ofuse, involving treatment in the patient's lung region, the patient ispositioned head-first with his shoulders beyond the track 228 so thattreatment occurs outside the shell 212.

As used herein, negative pitch refers generally to the lowering ordipping of the pod 200 distal end, while positive pitch refers generallyto the raising of the pod 200 distal end. Negative roll refers generallyto the counterclockwise rotation of the pod 200, while positive rollrefers generally to the clockwise rotation of the pod 200. Negative yawrefers generally to the rotation of the pod 200 about Axis-6 to theleft, while positive yaw refers generally to the rotation of the pod 200about Axis-6 to the right.

The shell 212 is preferably sufficiently long and wide to receive mostor all of the body of a human patient lying on it in any position, suchas, for example, the supine or prone positions. The structural shell 212length from Axis-6 to the distal edge 216 without attachments istypically in the range of about 75 cm to about 175 cm, often about 80 cmto about 125 cm, depending on the intended patient application specificsize (e.g., pediatric) and/or gantry size. In one embodiment, the lengthof the shell 212 from Axis-6 to the distal edge 216 is on the order of90 cm. As used herein, Axis-6 refers to the axis of the positioner 114that extends vertically through the attachment at the final yaw axis(e.g., wrist) of the positioner 114 (e.g., in the embodiment shown inFIGS. 2 and 3, the wrist comprises the swivel joint 152 at the distalend 116 of the robotic arm 150), thereby allowing yaw rotation of thepatient pod 200.

The overall longitudinal length of the shell 212 (i.e., between shellproximal edge 214 and shell distal edge 216) is typically in the rangeof about 90 cm to about 235 cm, often about 95 cm to about 175 cm. Inone embodiment, the overall longitudinal length of the shell 212 isabout 106 cm. The outer diameter of the shell 212 is typically in therange of about 35 cm to about 65 cm, often about 35 to about 55 cmdepending on the intended patient application specific size (e.g.,pediatric, large patient, etc.) and/or available treatment energy. Inone embodiment, the outer diameter of the shell 212 is about 46 cm.

In one embodiment, the shell 212 has a non-metallic (e.g., carbon fiber)composite construction that facilitates radiation beam treatmentsthrough the shell 212. Any number of imaging simulators known in the art(e.g., computed tomography imaging (CT), positron emission tomography(PET), magnetic resonance imaging (MRI), cone beam imaging. etc.) can beused to account for the treat-through material of the shell 212. As usedherein, the term “treat-through” refers generally to physical propertyof a material or surface that allows radiation beams to be irradiatedthrough a surface, and thereby deliver prescribed radiation doses from aradiation source, through a surface, and into a targeted area within thepatient on the other side of the surface. Treat-through properties aregenerally measured or quantified in terms of molecular equivalence ofwater. As used herein, the term “non-treat through” refers generally tothe physical property of a material or surface that does not allowradiation beams to be irradiated through a surface. Areas of the shell212 made of non-metallic materials are generally referred to astreat-through surfaces or zones.

As used herein, water equivalency refers generally to the effect of anabsorbing material on proton beam range relative to water. With respectto the treat-through sections, zones, or surfaces described herein,water equivalency is measured with respect to radiation beams that areperpendicular to the penetrable surface.

In one embodiment, illustrated in FIG. 4C, the shell 212 comprises acore material 240 encapsulated in a structural skin 242. The corematerial 240 can comprise any suitable low density materials known inthe art, such as, for example, structural foam or the like. Thestructural skin 242 can comprise any suitable firm, lightweight materialknown in the art, such as, for example, carbon fiber, spectra fiber,etc.

U.S. Provisional Application No. 60/583,063, filed Jun. 25, 2004, titledMETHOD AND DEVICE FOR REGISTRATION AND IMMOBILIZATION, the disclosure ofwhich is hereby incorporated in its entirety herein by reference,discloses some suitable materials from which the shell 212 can beconstructed.

In one embodiment, the shell 212 is made from polyvinylchloride (PVC) orthe like. In another embodiment, the shell 212 is made from fiberglassor the like. In still another embodiment, the shell 212 comprises anyknown suitable low density foam or the like.

In one embodiment, the shell 212 is constructed of composite skinscomprising polyethylene fibers embedded in an epoxy resin and alow-density polystyrene foam (Styrofoam®) core. A list of some of thematerials that can be used in manufacturing the shell 212 appears inTable I below.

# Matrix Fiber Type Fiber Structure 1 high impact polystyrene none n.a.(HIPS) 2 polymethylmethacrylate none n.a. (PMMA) 3 polycarbonate (PC)none n.a. 4 polyvinylchloride none n.a. (PVC) 5 polyethylene (PE) nonen.a. 6 epoxy resin none n.a. 7 epoxy resin fiberglass random 8 epoxyresin fiberglass woven 9 epoxy resin aramid woven 10 epoxy resin UHMW PEunidirectional tape 11 epoxy resin carbon twill woven 12 epoxy resincarbon unidirectional tape 13 epoxy resin ultrahigh modulusunidirectional tape carbon

In one embodiment, the carbon fiber composites, each woven ply of alay-up is approximately 0.25 mm thick. In one embodiment, the compositelay-up is approximately 50% fiber and 50% resin by weight. In oneembodiment, the fiber content of the composite is maximized while theresin content is minimized. In one embodiment, the shell 212 of the pod200 is made from the composite material Spectra, which is available fromHoneywell Performance Fibers in Colonial Heights, Va.

In one embodiment, at least one of the extension tracks 226, 228 is madefrom any suitable metal known in the art, such as, for example,aluminum. The use of metal, however, results in non-treat through zonesor areas. As such, the use of metal structures is generally limited inorder to minimize non-treat through surfaces. In another embodiment, atleast one of the tracks 226, 228 is made from a suitable non-metalmaterial known in the art, such as, for example, a carbon composite.

The extension tracks 226, 228 are advantageously positioned at the shelledges 214 and 216 of the pod 200, thereby facilitating radiationtreatment through the support shell 212 of the pod 200. The positioningof the extension tracks 226, 228 at the shell edges 214, 216 alsofacilitates the attachment of one or more pod extensions to the pod 200as explained in further detail below.

In one embodiment, the extension tracks 226, 228 are rounded such thatfor certain treatment positions, the patient shall not experience painor discomfort as the result of his contact with the track 226 or 228.The extension tracks 226, 228 preferably comprise interface extensionsthat are approximately flush with the inside surface 218 of the shell212. In one embodiment, the maximum step or vertical distance betweenthe inner surface 218 and the track interface extension is about 1 cm.

Extension tracks 226, 228 allow one or more pod extensions to beconnected to the pod 200, and provide modularity to the overall design.For example, track 228 can accommodate multiple head extensions andallows for 2-pi head and neck treatments. The modularity of the podcomponents and optional pod extensions accommodate multiple patientpositions within the pod 220, such as, for example, both head-first andfeet-first treatment positions. The pod 200 also accommodates treatmentpositions where the patient lies on his back, side, stomach, or anyvariations thereof. It will be noted that actual position of the patientwithin the pod 200 will depend on various factors, such as, for example,the radiation treatment protocol, as determined by the physician and/orradiation physicist, and the physical characteristics of the patient.

With reference to FIGS. 4A, 4B, and 6, in one embodiment, positioner-podconnector 234 is a rigid base member that allows connection to anypatient positioner 114, such as, for example, via the distal, workingend 116 of the positioner 114. The connector 234 comprises a positionerinterface clamping plate 236 for interfacing and attaching the pod 200to the patient positioner 114. The clamping plate 236 comprises aplurality of female ends 238 arranged in a circular pattern forreceiving bolts or other suitable fastening devices, thereby fixedlysecuring the pod 200 to the positioner 114. This particular embodimentof the clamping plate 236 is well suited for accommodating the boltpattern available on the KUKA KR500-L420 robotic positioner.

In one embodiment, the connector 236 (e.g., clamping plate) protrudesinto the shell 212 with a height H of approximately 1.75 inches, extendslongitudinally L along the shell 212 approximately 12 inches over therobot connection, and has a width W of approximately 11 inches. Inanother embodiment (not shown), the connector is integrated into theshell 212 and is flush to the contour of the inside surface of the shell212.

It will be noted that the pod 200 and any mechanical device mountedthereto should be positioned to avoid collision with the positioner 114during yaw treatment angles. The distance between the inside surface 218of the shell 212 and the connector 234 is typically in the range ofabout 5 mm to about 35 mm, often about 12 mm to about 25 mm. In oneembodiment, the distance between the inside surface 218 of the shell 212and the connector 234 is about 19 mm.

The patient pod 200 can comprise one or more attachments, extensions,adapter plates, or the like, or combinations thereof (collectively, “podattachments”). In one embodiment, shown in FIG. 4A, the pod 200comprises a cantilevered head rest extension 310 and a robot end, footrest extension 320. In another embodiment, shown in FIG. 2, the pod 200comprises a supine head extension 258 and a robot end extension 320.

With reference to FIGS. 7A-7G, one or more pod attachments can beremovably attached to one or both of the pod extension tracks 226, 228.In one embodiment, no tool is required to attach or remove the podattachments to the extension tracks 226, 228 of the pod 200. The podattachments preferably comprise treat-through materials and surfaces.

While these pod attachments can have treat-through surfaces that vary inwater equivalent thickness, it is preferred that the treat-thoughtsurfaces not vary in water equivalent thickness with a gradient greaterthan about 0.5 mm water equivalent thickness/mm along any transversedistance. The gradient limits will define design edge effects, thicknesschanges, and material transitions, as well as general manufacturingtolerances such as voids and material surface imperfections. In oneembodiment, the attachments have water equivalencies of no more thanabout 2 cm. In one embodiment, the shell 212 has about a 25 mm widenon-treat through region due to the mounted attachment track 226 or 228.It will be noted that the certain embodiments where the tracks 226, 228are made of metal, the tracks are non-treat through, whereas in certainother embodiments where the tracks 226, 228 are made of non-metalmaterials, such as, for example, carbon fiber, the tracks 226, 228provide treat-through zones. As with the shell 212, certain podattachments can comprise up to about a 25 mm wide non-treat throughregion due to the tracks 226, 228.

With reference to the embodiments shown in FIGS. 7A-7G, each of the podattachments 270, 280, 290, 300, 310, 320, 330 comprise an extensiontrack engaging end 262 which interfaces and connects with extensiontracks 226 and/or 228. The track engaging end 262 comprises an upper lip264 and a lower lip 266, where the space between lips 264 and 266 isapproximately equal to the distance between the inner and outerdiameters of extension tracks 226 and 228. The upper and lower lips 264and 266 each comprise a plurality of apertures 268, where each upper lipaperture is aligned with a corresponding lower lip aperture along avisualized radius extending outward from the center of thehemi-cylindrical shell 212. In one embodiment, the apertures 268 aredrilled or molded into locations within the track engaging end 262 toalign with the extension track apertures 230 or 232 along a visualizedradius extending outward from the center of the hemi-cylindrical shell212 when the track engaging end 262 engages with tracks 226 or 228. Inone embodiment, the attachment 270 is adjustably fastened to attachmenttrack(s) 226 or 228 by means of removable pins, bolts, or equivalentsthereof, slotted or screwed through the radially aligned apertures 230,232, 268.

With reference to FIG. 7A, in one embodiment, the pod attachmentcomprises a short, flat attachment 270 with a length of about 30 cm anda width of about 23 cm. Attachment 270 facilitates positioning thepatient at isocenter for head treatment including vertex with minimalshoot through material and permits 5-degree pitch and roll corrections.Attachment 270 comprises treat-through section 271 and treat-throughedges 272, 273.

With reference to FIG. 7B, in one embodiment, the pod attachmentcomprises a long, flat attachment 280 with a length of about 48 cm and awidth of about 23 cm. Attachment 280 facilitates positioning theENT/shoulder region away from the any non-treat through pod attachmenttracks 226, 228. Attachment 280 comprises treat-through section 281 andtreat-through edges 282, 283.

With reference to FIG. 7C, in one embodiment, the pod attachmentcomprises a shell leg or head extension attachment 290 that has adiameter approximately the same as the pod shell 212 and that isapproximately 67 cm long, thereby allowing the pod 200 to accommodatepatients who are 75 inches tall. Attachment 290 comprises an end-stop orcap 294 against which the patient's feet can be placed. Attachment 290comprises treat-through section 291, treat-through edges 292, 293,non-treat through section 295 and non-treat through edges 296, 297.

With reference to FIG. 7D, in one embodiment, the pod attachmentcomprises a flat extension 300 that is about 40 cm long and about 36 cmwide. Extension 300 comprises treat-through section 301, non-treatthrough sections 302, 303, 304, and non-treat through edges 305, 306.Here, section 301 is a head-rest region, while sections 302, 303, 304makeup the immobilization device attachment region. In one embodiment,extension 300 accommodates any number of immobilization devices andtechniques, described in further detail below. For example, in oneembodiment, extension 300 can be dimensioned to facilitate optionalcranial ring immobilization mountings.

With reference to FIG. 7E, in one embodiment, the pod attachmentcomprises a short, head rest extension 310. Extension 310 comprisestreat-through section 311 and treat-through edges 312, 313, 314.

With reference to FIG. 7F, in one embodiment, the pod attachmentcomprises a robot end extension 320 that is chamfered at an angle ofapproximately 45-degrees relative to a visualized, longitudinal axisextending between the proximal and distal extension tracks 226 and 228,beginning at about 19 cm from Axis-6 up to distance of about 43 cm fromAxis-6, thereby preventing collision with the patient positioner 114.Extension 320 does not have any treat-through sections or edges; rather,sections 321, 322, 323 and edges 324, 325, 326 are all non-treatthrough.

With reference to FIG. 7G, in one embodiment, the pod attachmentcomprises a prone headrest 330 to accommodate prone treatments. Theprone headrest defines an face-through hole 331 through which thepatient can place his face. The prone headrest 330 comprises non-treatthrough sections 332, 333.

Any number of immobilization devices can be used with the patient pod200. With reference to FIG. 5, in one embodiment, the modular patientsupport system 199 comprises the patient pod 200 and an immobilizationdevice, further comprising a rigid moldable foam cradle 350 bonded tothe pod shell top surface 218. Cradle 350 conforms to a selected region(e.g., back, front, or side) and comprises a mold 352 conforming exactlyto the patient's body for securely holding the patient in positionduring radiation treatments. The rigid foam cradle 350 can be formed ina manner similar to that employed in U.S. Pat. No. 4,905,267, titledMETHOD OF ASSEMBLY AND WHOLE BODY, PATIENT POSITIONING AND REPOSITIONINGSUPPORT FOR USE IN RADIATION BEAM THERAPY SYSTEMS, the disclosure ofwhich is hereby incorporated in its entirety herein by reference.

In one approach, an expandable, liquid foaming agent known as ACMMfoaming agent 325, available from the Soule Co., Inc., Lutz, Fla. orSmithers Medical Products, Inc., Akron, Ohio, is used to form the rigidfoam cradle 350. In one approach, the foaming agent is painted onto theshell top surface 218. After the foaming agent is introduced within theshell, the patient is positioned within the shell where he laysmotionless for approximately 15 minutes until the foaming agent hascooled to room temperature and the patient body mold 352 is formed.

The foam between the patient and the pod can be mechanically stabilizedto prevent the foam from moving and displacing the patient between orduring treatments. In one approach, the foam is placed inside a verythin plastic bag. In another approach, the pod is lined with alow-density foam sheet. In still another approach, a very thin,disposable, plastic shell is inserted into the pod before applying thefoam chemicals. In yet another approach, there is no lining between thefoam and pod; rather, the inner pod surface is made very smooth by thecomposite layers on a high quality aluminum mold. In still anotherapproach, the inner surface of the pod is coated with Teflon or anothernonreacting substance.

Other suitable immobilization devices that can be used with the patientpod 200, with or without any flat extensions, include, but are notlimited to, bite blocks, face masks, vacuum bags, halos or cranialrings, localizer Z-frame boxes, triangular leg pillows, foam inserts, orthe like, or combinations thereof. Bite block mouthpieces are preferablycompatible with any existing MRI “Head Coils.” In one embodiment, thebite block frame preferably limits translational movement of any pointin the treatable volume to no more than about 1.0 mm given the force of30 pounds in any direction. In another embodiment, the bite block framelimits head rotations to less than or equal to about one-degree in anydirection under a force of about 30 pounds in any direction. In oneembodiment, the bite block frame mounts to the shell 212 and/or any podattachments via an existing vacuum system providing approximately 9 psi.

With respect to the various pod attachments described above, the weightof any of the pod attachments preferably does not exceed about 30 poundsin weight, thereby making it easier for an individual to carry andinstall the pod attachment to the pod shell 212. Pod attachments mountedon the side near Axis-6 are preferably angled along the robotic arm orpositioner to eliminate injury or collision.

In one embodiment, the pod 200 is capable of supporting a 400 pounddistributed patient load (not including any immobilization devices) withthe patient center of gravity not to exceed 37 inches from Axis-6. Thepod 200 is preferably capable of supporting a 300 pound end load (withor without extensions) to accommodate an individual seated on thecantilevered end 216. In one embodiment, the pod 200 is capable ofsupporting a patient load of 300 lbf, an immobilization load of 50 lbf,and a 200 lbf longitudinal load located on the extensions.

In one embodiment, the pod 200 is preferably capable of supporting awater phantom load of 275 pounds (125 kg) at the proximal extensiontrack 226.

In one embodiment, the pod 200 is capable of supporting animmobilization and patient load of up to approximately 150 poundslocated on the attachments with a deflection of no more than 2 mm.Extensions are preferably capable of supporting a 300 pound load at theend in the event a person was to sit on the extension, thereby resultingin a pod with extension that is not overly flexible.

With continued reference to FIGS. 4A and 4B, in one embodiment, thedeflection of the shell 212 at the cantilevered end 216 due to patientload is preferably less than or equal to about 5 mm. In one embodiment,such deflection can be compensated for during treatment using anexternal measurement system that will correct inherent mechanicalerrors. In one embodiment, the pod 200 is accompanied by or includes aninclinometer as safety feature to prevent the positioner 114 fromproducing angular deflections great than about ±5.5 degrees from thehorizontal. An inclinometer or tilt sensor comprises any device,typically electro-mechanical, that senses the angle of an object withrespect to gravity.

The vertical deflection of the patient pod 200 at the distal,cantilevered end (with or without extensions) due to a 300 pound patientdistributed load and 50 pound immobilization load is preferably lessthan about 4 mm. The lateral deflection of the pod 200 (with or withoutextensions) due to a patient lateral load of 100 pounds is preferablyless than about 0.5 mm. It will be noted that these types of verticaland lateral deflections can be compensated for during treatment by usingan external measurement system that corrects inherent mechanical errors.

All table constituent materials and components preferably withstand anaverage daily radiation dose of approximately 9,000 rads, 5 days perweek, 52 weeks per year, over a 20 year lifetime. All hardware andcomponents preferably operate normally in the temperature environment of40-95 degrees F. with a relative humidity of 25-78%.

The treat-through surfaces of the pod 200 preferably do not vary inthickness with a gradient greater than about 0.5 mm water equivalentthickness per mm along any transverse distance. The edges oftreat-through areas of the pod 200 are preferably less than about 0.5 mmwater equivalent thickness. In one embodiment, the treat-throughthickness of the pod 200 preferably has a water equivalency of less thanapproximately 2 cm.

Components of the pod 200 positioned between the patient and theradiographic image receptor preferably have an aluminum equivalence lessthan or equal to about 5 mm per FDA CFR part 1020.

With continued reference to FIGS. 4A and 4B, in one embodiment, thegeometry and size of the pod 200 accommodates a CT scanner with aphysical aperture of 68 cm and an image reconstruction diameter of 48cm. The treat-through surfaces in the shell 212 preferably do not varyin thickness. Here, the edges of treat-through areas are preferably lessthan about 0.5 mm water equivalent thickness. In one preferredembodiment, the thickness of the shell 212 has a water equivalency of nomore than about 2 cm.

The pod attachments preferably have an aluminum equivalence of about 5mm per FDA CFR Part 1020 (Compliance determined by x-ray measurementsmade at a potential of 100 kilovolts peak and with an x-ray beam thathas a HVL of 2.7 mm of aluminum). As used herein, aluminum equivalencyrefers to the thickness of aluminum (type 1100 alloy) affording the sameradiographic attenuation, under same specified conditions, as thematerial in question. It will be noted that the modular patient supportsystem 199 is preferably capable of accommodating a 65 cm×60 cm×60 cmwater phantom at the robot end.

In one embodiment, the radiation treatment system 100 comprises anexternal measurement or vision system, which further comprises visionsystem markers. The vision system markers are preferably mounted to thenon-treat through areas, such as, for example, tracks 226, 228 made ofmetal.

C. Patient Pod with Tapered Edge Configuration

In accordance with one embodiment described herein, there is provided apatient pod with a tapered edge configuration that reduces edge effectsassociated with abrupt changes in the water equivalency in the radiationbeam path.

For certain radiation treatment protocols, radiation beams of aprescribed intensity are delivered from lateral positions. In certaininstances, for example, where the radiation beam is delivered from alateral position that is well above patient pod, the radiation beam doesnot have to be delivered through the patient pod. In another scenario,where the radiation beam is delivered from a lateral position that iswell below the patient pod, the radiation beam can pass through a podshell surface of uniform density or water equivalency. There aresituations, however, where the radiation beam traverses one or both ofthe lateral edges (e.g., lateral edge 222 or 224 of the pod shell 212depicted in FIG. 4A). An abrupt transition or change in the waterequivalency between the pod shell and the space above the pod shelllateral edge can result in radiation beams having intensities that arenon-uniform or difficult to predict. The effects of any abrupttransitions in the water equivalency in the beam path referred to hereinas edge effects.

Sections of the lateral edges of the patient pod can be tapered toreduce or minimize the edge effects. With reference to FIG. 4C, in oneembodiment, the lateral edge 222 comprises a gradually tapered edge 243and a longitudinally-extending rail 299. The tapered edge 243 comprisesan inner surface 245 that tapers outward beginning at lower edge 244 andends at upper edge 248. Tapered edge 243 also comprises an outer surface247 that tapers inward beginning at lower edge 246 and ends at upperedge 248. Surfaces 245 and 247 ultimately converge at upper edge 248.The location and degree of tapering of edges 244, 246 can be varied asneeded to reduce any edge effects.

With reference to FIGS. 4A-4C, the tapered edge 243 is typically taperedwith a gradient from about 0.1 mm water equivalency/mm to about 5 mmwater equivalency/mm, depending on accuracy requirements andrepeatability of immobilization devices. In one embodiment, the taperedportion 243 is tapered with a gradient of about 0.5 mm waterequivalency/mm.

The lateral edges of the pod are relatively thin, thereby minimallyperturbing any therapeutic proton beams passing through or near any ofthe lateral edges.

The low-density rail 299 covers tapered edge 243, and thereby protectsthe patient and radiation treatment providers from the upper edge 248which tends to be a sharp edge. With reference to exemplary shelllateral edge 222 illustrated in FIG. 4C, the lateral edge 222 generallycomprises an inferior portion that is complementary to the shape of thetapered edge 243 and a superior portion that is generally rounded orblunt.

The rail 299 preferably comprises a low-density material, such as, forexample, epoxy with microspheres, extruded or molded plastics (nylon,urethane, etc.), rubber, or the like, or combinations thereof. In oneembodiment, the rail 299 maintains the 0.5 mm/mm water equivalentgradient of the shell 212.

In one embodiment, the rail 299 is removably secured to the shelltapered edge 243 via any attachment mechanism known in the art, such as,for example, an interlocking receiver molded into the shell 212 forpositive locating and holding of the rail 299. In another embodiment,the rail 299 simply sits the tapered edge 243 without the aid of anyattachment mechanisms. In yet another embodiment, the rail 299 ispermanently secured to the tapered edge 243 using any known suitableattachment mechanism, such as, for example, epoxy with micro-spheres.Patient safety and comfort are preferably integrated with eachembodiment. Several transitions, methods, and materials can be used toachieve specified gradient, level of safety and patient comfort, suchas, for example, replaceable handrails or pliable edges.

D. Aimable Volume of Modular Patient Support System

The aimable volume will generally depend on the orientation of thepatient pod 200 and the patient positioner 114 that interfaces with thepatient pod 200 along the orthogonal translational and rotational axes.

FIG. 8 provides a schematic partial cross-sectional side view of theshape of the aimable volumes 352, 354 (hashed) for the pod shell 212.Here, the pod 200 has a thickness of about 1.9 cm above thepositioner-pod connector 234. For any yaw angle up to 93 degrees, withor without pitch and roll corrections, the aimable volume (made up ofvolumes 352 and 354) is approximately a 40 cm tall by 50 cm widetrapezoidal volume extending about 120 cm along the table from Axis-6 toa distal height of about 31.9 cm. One half of the aimable volume isaccessible in 93-degree vertex positions when the bottom of the aimablevolume is at isocenter. For example, in one embodiment, in a left vertexposition at a 93-degree yaw, the left half of a patient's head(positioned face up with head at end of pod 200) is inaccessible becauseof maximum robot reach. Positioning the pod 200 to a right vertex allowsaccessibility to this left half. The patient himself may be positionedwith a lateral shift to eliminate this. Here, the aimable volumes 352,354 for vertex treatments typically begin about 3 cm off of shellsurface 218.

It will be understood that the invention described herein, and thecomponent parts thereof, can be sued in any number of combination oftreatment systems, including, but not limited to, proton treatment,conventional radiation treatment, and imaging systems (e.g., CT, PET,MRI, cone beam, etc.).

While the present invention has been illustrated and described withparticularity in terms of preferred embodiments, it should be understoodthat no limitation of the scope of the invention is intended thereby.Features of any of the foregoing devices and methods may be substitutedor added into the others, as will be apparent to those of skill in theart. The scope of the invention is defined only by the claims appendedhereto. It should also be understood that variations of the particularembodiments described herein incorporating the principles of the presentinvention will occur to those of ordinary skill in the art and yet bewithin the scope of the appended claims.

What is claimed is:
 1. A patient pod configured to support a patientduring a medical treatment, the pod comprising: a semi-cylindrical shellstructure configured to be concave upward to provide a patient space,the shell structure extending transversely between a first lateral edgeand a second lateral edge and extending longitudinally between aproximal edge and a distal edge, the shell structure comprising a top,concave surface and a bottom, convex surface that faces outward, awayfrom the patient space; the top, concave surface configured to beparallel to the bottom, convex surface, except at the first and secondlateral edges; the first and second lateral edges being tapered toreduce the effect of changes in the water equivalency between the shellstructure and a space above the shell structure; the top, concavesurface comprising a separate, flat, inwardly-facing portion that tapersaway from the top, concave surface of the shell structure to a narrowerupper tip, the bottom, convex surface comprising a separate, flat,outward facing portion that tapers away from the bottom, convex surfaceand converges to meet the flat, inwardly-facing portion at the narrowerupper tip.
 2. The patient pod of claim 1, further comprising: a proximalextension track configured for engagement with any of a number ofproximal pod attachments in order to extend the shell structure from theproximal edge; and a distal extension track configured for engagementwith any of a number of distal pod attachments in order to extend theshell structure from the distal edge.
 3. The patient pod of claim 1,wherein the separate, flat, inwardly-facing portion that tapers awayfrom the top, concave surface of the shell structure to a narrower uppertip and the bottom, convex surface comprising a separate, flat, outwardfacing portion that tapers away from the bottom, convex surface togethercomprise a tapered section of the patient pod.
 4. The patient pod ofclaim 3, wherein the patient pod further comprises at least two taperedsections.
 5. The patient pod of claim 3, wherein the tapered section istapered with a gradient from about 0.1 mm water equivalency/mm to about5 mm water equivalency/mm.
 6. The patient pod of claim 3, wherein thetapered section is tapered with a gradient of about 0.5 mm waterequivalency/mm.
 7. The patient pod of claim 3, further comprising alongitudinally-extending rail configured to cover the tapered section.8. A patient support configured to position a patient during a medicaltreatment, the support comprising: a shell extending in a transversedirection between a first tapered lateral edge and a second taperedlateral edge and extending in a longitudinal direction between aproximal edge and a distal edge, the shell comprising a top, concavesurface and a bottom, convex surface; the first tapered lateral edgecomprising a first separate, flat, inwardly-facing portion that tapersaway from the top, concave surface of the shell to a first narrowerupper tip and a first separate, flat, outward facing portion that tapersaway from the bottom, convex surface of the shell and converges with thefirst flat, inwardly-facing portion at the first narrower upper tip; andthe second tapered lateral edge comprising a second separate, flat,inwardly-facing portion that tapers away from the top, concave surfaceof the shell to a second narrower upper tip and a second separate, flat,outward facing portion that tapers away from the bottom, convex surfaceof the shell and converges with the second flat, inwardly-facing portionat the second narrower upper tip.
 9. The patient support of claim 8,further comprising a first rail configured to cover the first taperedlateral edge and a second rail configured to cover the second taperedlateral edge.
 10. The patient support of claim 9, wherein the first railand the second rail have a water equivalent thickness of about 0.5 mm ofwater at locations where a radiation beam passes through.
 11. Thepatient support of claim 9, wherein the first rail comprises an inferiorportion that is complementary in shape to the first tapered lateral edgeand the second rail comprises an inferior portion that is complementaryin shape to the second tapered lateral edge.
 12. The patient support ofclaim 9, wherein the first rail and the second rail each comprise asuperior portion that is rounded.
 13. The patient support of claim 9,wherein the first rail and the second rail comprise at least one ofepoxy, nylon, urethane, and rubber.
 14. The patient support of claim 8,further comprising a rail removably connected to at least one of thefirst tapered lateral edge and the second tapered lateral edge.
 15. Thepatient support of claim 14, further comprising an interlocking receiverto removably secure the rail to the shell.
 16. The patient support ofclaim 8, further comprising means for engaging a shell attachment toextend the shell in the longitudinal direction.
 17. The patient supportof claim 16, wherein the engaging means comprises an extension trackconfigured for engagement with a shell attachment.
 18. The patientsupport of claim 17, wherein the extension track is configured to engagea shell attachment having an upper lip spaced from a lower lip by adistance that is approximately equal to a distance between an innerdiameter and an outer diameter of the extension track.